The invention relates generally to medical connectors of the type used in the handling and administration of parenteral fluids, and more particularly, to a needleless connector employing a valve mechanism that compensates for negative fluid displacement, i.e., drawing of fluid into the outlet end of a connector, during deactuation of the valve.
Within this specification the terms, “negative-bolus effect,” “positive-bolus effect,” and “no-bolus effect” are used to describe the operating characteristics of medical connectors during deactuation of the valve mechanisms contained within the connectors. Negative-bolus effect describes the condition during which fluid is drawn into the connector during deactuation. Positive-bolus effect describes the condition during which fluid is flushed out of the connector during deactuation. No-bolus effect describes the condition during which fluid displacement is neutralized and fluid is neither drawn into nor flushed out of the connector during deactuation.
Needleless medical connectors for injecting fluid into or removing fluid from an intravenous (IV) system are well known and widely used. Conventional needleless medical connectors generally include a housing having an inlet port and an outlet port. The inlet port is sized to receive a blunt male cannula, such as a male Luer taper. Disposed within the inlet port is a valve mechanism that provides access to a fluid path that communicates with the outlet port. In some connectors, the fluid path is defined by the internal boundaries of the connector housing, in other connectors it is defined by an internal cannula or hollow spike, still in others, the fluid path is defined by a compressible tubular body which carries the valve mechanism. The outlet port of the connector is typically connected to IV tubing which in turn is connected to an IV catheter that communicates with a patient's venous system.
Many needleless medical connectors create fluid displacement during actuation and deactuation of the valve mechanism. During actuation, the blunt male cannula is inserted into the inlet. In some connectors, the cannula passes through the valve mechanism to establish fluid communication with the fluid path. In other connectors, the cannula merely displaces the valve mechanism, without penetrating it, in order to establish fluid communication with the fluid path. In either case, the volumetric capacity of the fluid path is often reduced by the insertion of the blunt cannula. Subsequently, when the blunt cannula is removed from the connector, the volumetric capacity of the fluid path increases. This increase in the volumetric capacity may create a partial vacuum in the fluid path that may draw fluid into the connector from the outlet end. As previously mentioned, the effect of drawing fluid into the connector in this manner is referred to as a “negative-bolus” effect in that a quantity, or “bolus,” of fluid is drawn into the partial vacuum or negative pressure location; i.e., the connector.
A negative-bolus effect is undesirable in that the partial vacuum created within the connector may draw fluid from the IV tubing. The IV tubing in turn draws fluid from the IV catheter which in turn draws fluid, e.g., blood, from the patient's venous system.
The negative-bolus effect may be reduced by undertaking operational safeguards. For instance, prior to the removal of the blunt cannula from the connector, the IV tubing may be clamped off between the connector output port and the IV catheter. This prevents the backup of blood through the IV catheter. If a syringe with a blunt cannula tip is used to inject fluid into the inlet port of the valve, the syringe may be continually depressed while the syringe is disengaged from the connector. The continued depression of the syringe injects fluid into the fluid path to fill the increasing volume thereby reducing the chance of a partial vacuum forming in the fluid path and a negative bolus. However, both of these approaches are undesirable in that the operator must remember to perform an additional step during removal of the syringe or other device from the connector rather than the steps being taken automatically by the connector.
The negative-bolus effect may also be reduced by the design of the medical connector. As previously mentioned, some medical connectors include an internal cannula or hollow spike housed inside the connector body. The internal cannula or spike is positioned to open a septum upon depression of the septum onto the internal cannula or spike by a blunt cannula. The internal cannula or spike has a small orifice at the top and upon depression of the septum is put in fluid communication with the blunt cannula. The internal cannula or spike provides a generally fixed-volume fluid-flow path through the connector. Thus, as the septum returns to its closed position the partial vacuum formed within the connector is not as strong as the vacuum formed in a connector having a more volumetrically dynamic fluid path. A disadvantage of typical connectors having an internal cannula or spike is a lower fluid-flow rate. This low flow rate is caused by the small orifice in the cannula or spike. Additionally, it has been noted that with the connector design having a fixedly-mounted internal spike and a movable septum that is pierced by that spike to permit fluid flow, such pierced septum may be damaged with multiple uses and a leaking connector may result.
Other connectors provide a valve mechanism that includes a flexible silicone body and a rigid spring leaf positioned about an internal cannula. Upon depression of the valve mechanism by a blunt cannula, the internal cannula forces the leaves of the spring leaf apart, the leaves in turn force the top of the body apart and open a slit contained therein. The opening of the slit establishes fluid communication between the blunt cannula and the internal cannula. The body includes a side reservoir that expands upon depression of the valve mechanism and receives fluid. Upon deactuation of the valve mechanism the reservoir collapses between the connector housing and the spring leaf and fluid is forced out of the reservoir into the internal cannula. This displacement of fluid may fill the partial vacuum being formed by the deactuation of the valve mechanism and thus reduce the possibility of fluid being drawn into the connector.
Although these connectors may reduce the negative-bolus effect, they have several disadvantages. First, during periods of nonuse, residual fluid left within the collapsed reservoir is likely to dry and adhere to the leaf spring. This may cause particulate to enter the fluid path during subsequent actuation or may even prevent the reservoir from expanding during subsequent actuation. Second, the connector employs a complex two-part valve mechanism that requires an internal cannula for actuation and deactuation. The complexity of this device lends itself to manufacturing difficulties and increased manufacturing costs. Third, during actuation of the valve mechanism, the leaves of the rigid spring leaf may cut through the body and cause a leak.
Hence, those concerned with the development of medical connectors have recognized the need for a medical connector having a valve mechanism that avoids the negative-bolus effect by producing either a positive-bolus effect or a no-bolus effect. The need for a medical connector that provides these effects without sacrificing fluid-flow rate or structural simplicity has also been recognized. The present invention fulfills such needs and others.